The infections very often complicate the course of autoimmune rheumatic diseases. In diagnostic of septic complications in rheumatic patients the new biomarkers of infections can have a decisive importance. The procalciotonine test is one of them. The issue was to evaluate the diagnostic informativity of this test. The sample included 93 patients. The examination was applied to 65 patients with rheumatic diseases. Among them, 13 patients had bacterial infections. The group consisted of 33 patients with rheumatoid arthritis, 11 patients with systemic lupus erythematous, 6 patients with systemic angiitis, and 15 patients with other rheumatic diseases. The comparative group included 27 patients of cardio-therapeutic profile and 8 of these patients had bacterial infections. The procalcitonine test was applied with quantitative electrochemiluminescent technique. In patients with rheumatoid arthritis the mean levels of procalciotonine test consisted 0.10±0.J3 ng/ml; with systemic lupus erythematous - 0.08±0.06 ng/ml; with systemic angiitis - 0.2 2±0.2 ng/ml; with other rheumatic diseases - 0.12±0.15 ng/ml; of cardio-therapeutic profile without infections - 0.08±0.06 ng/vl/ With threshold of procalcitonine test higher than 0.5 /ml the sensitivity to diagnostic of infections consisted of 58%, specificity - 94% in the group with rheumatic diseases. The procalciotonine test in case of no infection process with values higher than 0.5 ng/ ml was detected in three patients. The evaluation of dependence of sensitivity and specificity for procalciotonine test and C- reactive protein the area under curve of procalcitonine test was larger in patients with rheumatic diseases (0.85 against 0.79) and in patients of cardio-therapeutic profile (0.92 against 0.90). The quantitative procalcitonine test is the best technique to detect septic complications in rheumatic patients.